Protective coating and metal structure

ABSTRACT

A protective coating for protecting a component of a gas turbine engine or such from wear is provided with a base coating consisting essentially of metal and including a pore, and a spherical particle filling the pore, at least a surface of which consists essentially of a ceramic.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part Application of PCT InternationalApplication No. PCT/JP2006/304558 (filed Mar. 9, 2006), which in turnbased upon and claims the benefit of priority from Japanese PatentApplication No. 2005-073792 (filed Mar. 15, 2005), the entire contentsof which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a protective coating for protectingcomponents of a gas turbine engine or such from wear and a metalstructure having wear resistance.

2. Description of the Related Art

A gas turbine engine carries out high-speed revolution under hightemperatures and its components rub against opposite components. Toprotect the respective components from wear, protective coatings are ingeneral formed on limited sites which are subject to wear. Theprotective coating is made of porous metal and fine pores thereof areimpregnated with lubrication oil. Japanese Patent Application Laid-openNo. 2002-106301 discloses a related art.

The gas turbine engine is used in a very broad temperature range. Duringa shutdown, it may go down to minus 50 degrees C. In such anenvironment, the lubrication oil tends to be solidified. On the otherhand, during operation, it may reach up to 250 degrees C., at which thelubrication oil could evaporate. Either case would give rise to aproblem with lubrication.

SUMMARY OF THE INVENTION

The present invention has been achieved in view of the above problem andhas an object for providing a protective coating having a lubricationfunction and a metal structure having wear resistance, both of which areenabled without any lubrication oil.

According to first aspect of the present invention, a protective coatingfor protecting a component from wear is provided with a base coatingconsisting essentially of metal and including a pore, and a sphericalparticle filling the pore, at least a surface of which consistsessentially of a ceramic.

Preferably, the base coating is formed by executing discharge depositionfrom a working electrode consisting essentially of the metal onto thecomponent with applying the component as a workpiece. More preferably,the protective coating is further provided with a fusion part coveringan interface toward the component, the fusion part having a gradingcomposition ratio grading toward the component. Still preferably, thefusion part is 3 μm or more and 20 μm or less in thickness.

According to a second aspect of the present invention, a componentapplied to a gas turbine engine is provided with a main body having asubject site, a base coating covering the subject site, which consistsessentially of a metal and includes a pore, and a spherical particlefilling the pore, at least a surface of which consists essentially of aceramic.

Preferably, the base coating is formed by executing discharge depositionfrom a working electrode consisting essentially of the metal onto themain body with applying the main body as a workpiece. More preferably,the component is further provided with a fusion part covering aninterface toward the main body, which has a grading composition gradingtoward the main body. Still preferably, the fusion part is 3 μm or moreand 20 μm or less in thickness.

According to a third aspect of the present invention, a metal structureapplied to a site subject to rubbing is provided with a main bodyconsisting essentially of a metal and including a pore, and a sphericalparticle filling the pore, at least a surface of which consistsessentially of a ceramic.

Preferably, the main body and the particle are formed by sintering amixed powder of a powder consisting essentially of the metal and apowder consisting essentially of the ceramic.

A protective coating having a lubrication function and a metal structurehaving wear resistance, both of which are enabled without anylubrication oil, are provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic drawing showing a component of an engine having aprotective coating in accordance with a first embodiment of the presentinvention, and FIG. 1B is a schematic drawing in which the protectivecoating is magnified;

FIG. 2 is a schematic drawing showing a process of forming theprotective coating;

FIG. 3 is a drawing showing a relation between thickness of a fusionpart and adhesion strength of a protective coating in a case where thecoating is formed by means of the process;

FIG. 4 is a drawing showing a relation between thickness of a fusionpart and deformation of the subject body in a case where the coating isformed by means of the process;

FIG. 5A is a schematic drawing showing a metal structure having aprotective coating in accordance with a second embodiment of the presentinvention, and FIG. 5B is a schematic drawing in which the protectivecoating is magnified; and

FIGS. 6A-6C are schematic drawings showing a process of forming theprotective coating.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Throughout the specification and claims, several terms are used inaccordance with the following definitions. The term “dischargedeposition” is defined and used as use of discharge in an electric sparkmachine for wearing an electrode instead of machining a workpiece todeposit a material of the electrode or a reaction product between thematerial of the electrode and a machining liquid or a machining gas onthe workpiece. Further, the term “discharge-deposit” is defined and usedas a transitive verb of the term “discharge deposition”.

In certain embodiments of the present invention, an electric sparkmachine (most of it will be not shown) is used for executing dischargedeposition. In discharge deposition, a subject body is set in anelectric spark machine as a workpiece thereof, and made closed to aworking electrode in a processing bath. Then, in a case of general sparkmachining, pulsing current is supplied from an external power source togenerate pulsing discharge between the workpiece and the workingelectrode so as to wear the workpiece, thereby the workpiece is machinedinto a shape complementary to a tip of the working electrode. Incontrast, in the discharge deposition, the working electrode instead ofthe workpiece is worn and a material of the working electrode, or areaction product between the material of the electrode and a machiningliquid or a machining gas is made deposited on the workpiece. Thedeposit thereby is not only adhered on the workpiece but also maysimultaneously undergo phenomena diffusion, weld and such between thedeposit and the workpiece and further among particles in the depositmutually by using energy of the discharge in part.

A first embodiment of the present invention will be describedhereinafter with reference to FIGS. 1 and 2.

A protective coating 1 in accordance with a first embodiment of thepresent invention is applied to an engine component 3 consistingessentially of a metal applied to a gas turbine engine or such. Theprotective coating 1 is formed on a subject portion 3 a as a site whichrubs against an opposite engine component, as shown in FIGS. 1A and 1B.

The protective coating 1 includes a base coating 7, which consistsessentially of a metal and is formed to be porous, and spherical hardparticles 9 embedded therein. Here, a preferable example of the metal isan alloy including Co (cobalt), Cr (chromium), and W (tungsten), whileany proper metal may be selected and applied thereto.

In fine pores 7 a of the base coating 7, the spherical hard particles 9are filled in a rotatable condition. The hard particles 9 consistessentially of Cr₂O₃ (chromium oxide) which is one of oxide ceramics. Aparticle size of the hard particles 9 is preferably 50 μm or less.

It may be modified so that not the whole of but at least surfaces of thehard particles 9 consist essentially of oxide ceramics. Alternatively,carbide ceramics, instead of oxide ceramics, may be applied thereto.

As shown in FIG. 2, the protective coating 1 is discharge-deposited byattaching the engine component 3 to a jig 13 as a workpiece of anelectric spark machine, having the engine component 3 closed to aworking electrode 11 in a processing bath of the electric spark machine,and generating pulsing discharge between a subject portion 3 a and theworking electrode 11 in an electrically insulating fluid S stored in theprocessing bath.

Here, the working electrode 11 is a molded body made by pressing amixture of a powder consisting essentially of the metal and the hardparticle 9 or the molded body treated with heat treatment so as to besintered at least in part. Meanwhile, the working electrode 11 may beformed by slurry pouring, MIM (Metal Injection Molding), spray formingand such, instead of pressing. By executing discharge deposition, themetal included in the working electrode 11 is deposited on theworkpiece. Further the deposited metal fuses together and/or carries outinterdiffusion in itself to form the base coating 7 to leave the finepores 7 a. Simultaneously the hard particle 9 included in the workingelectrode 11 is made filled into the pores 7 a of the base coating 7.The structure of the base coating 7 formed in such a way inherentlyallows the spherical hard particles 9 to rotate in the pores 7 a.

Further, at a boundary between the protective coating 1 and a base ofthe engine component 3, a fusion part (fusion layer) B in which thecomposition ratio grades in its thickness direction is formed. Thefusion part B is so constituted as to be 3 μm or more and 20 μm or lessin thickness by selecting a proper discharge condition at a time offormation of the protective coating 1. Meanwhile, the proper dischargecondition may be that a peak current is 30 A or less and a pulse widthis 200 μs or less, and more preferably that a peak current is 20 A orless and a pulse width is 20 μs or less.

Here, a ground on which the thickness of the fusion part B is 3 μm ormore and 20 μm or less is based on test results shown in FIG. 3 and FIG.4.

More specifically, in a case where coatings are formed on metal bases bymeans of discharge deposition on various discharge conditions, arelation between thickness of the fusion parts and adhesion strength ofthe coatings is as shown in FIG. 3. A novel first knowledge that theadhesion strength of the fusion part to the coating goes larger when thethickness of the fusion part is 3 μm or more could be obtained. Further,as the relation between the thickness of the fusion part and thedeformation of the base is as shown in FIG. 4, a novel second knowledgethat deformation of the base can be suppressed when the thickness of thefusion part is 20 μm or less could be obtained. Therefore, the thicknessof the fusion part B was set 3 μm or more and 20 μm or less so as toraise the adhesion strength of the protective coating 1 with suppressingthe deformation of the base of the engine component 3 from the novelfirst and second knowledge.

Meanwhile, horizontal axes of FIG. 3 and FIG. 4 indicate logarithms ofthicknesses of the fusion parts, a vertical axis of FIG. 3 indicatesdimensionless numbers of adhesion strengths of the coatings, and avertical axis of FIG. 4 indicates dimensionless numbers of deformationof the bases.

Next, actions and effects of the first embodiment will be describedhereinafter.

As the fine pores 7 a of the base coating 7 are filled with the hardparticles 9 in a rotatable condition, the hard particles 9 exposed outof the surface of the base coating 7 rotate within the fine pores 7 awhen the engine component 3 rubs against the opposite engine component5. Thereby the rotating hard particles 9 make the protective coating 1exhibit a lubrication action without lubrication oil. Therefore,regardless of whether the temperature of the atmosphere in use of theengine component 3 is high or low, adhesive wear of the engine component3 can be sufficiently suppressed.

Meanwhile, the present invention is not limited to the aforementionedfirst embodiment and can be enabled on the bases of various embodimentsdescribed below.

More specifically, instead of generating pulsing discharge in theelectrically insulating fluid S, pulsing discharge may be generated inan electrically insulating gas. Further, instead of forming theprotective coating 1 by discharge deposition, the protective coating 1may be formed by any other proper means.

A second embodiment of the present invention will be describedhereinafter with reference to FIG. 5 and FIG. 6.

As shown in FIGS. 5A and 5B, the metal structure 15 in accordance withthe second embodiment is a disk-like structure having wear resistanceused for an engine or such. A concrete structure of the metal structure15 is as described later. Meanwhile, an outer peripheral surface of themetal structure 15 is a site which rubs against an inner peripheralsurface of an opposite cylindrical engine component (one of oppositemetal components) 17.

More specifically, the metal structure 15 is provided with a structuremain body 19, which consists essentially of a metal and is formed to beporous. Here, a preferable example of the metal is one of Ni (nickel),Fe (iron) and Cu (copper), or an alloy consists essentially of two ormore thereof, while any proper metal may be selected and appliedthereto.

In fine pores 19 a of the structure base body 19, spherical hardparticles 21 are filled in a rotatable condition. The hard particles 21consists essentially of Cr₂O₃ (chromium oxide) which is one of oxideceramics. Alternatively, instead of the oxide ceramics, any carbideceramic may be applied thereto.

The metal structure 15 is formed by sintering mixed powder 23 of powderof the metal and powder of the oxide (or carbide) ceramic. Each particleof the powder of the ceramic is formed in a spherical shape. The metalstructure 15 is formed by three steps including a (i) filling step, a(ii) molding step, and a (iii) heating step.

More specifically, as shown in FIGS. 6A-6C, adding wax to the mixedpowder 23 and filling the mixed powder 23 in a mold die 25 are carriedout ((i) filling step). Here, the mold die 25 is provided with acylindrical die 27, an upper punch 29 provided above a die hole 27 h ofthe die 27 so as to be vertically movable, and a lower punch 31 belowthe die hole 27 h of the die 27 so as to be vertically movable. Next, asshown in FIG. 6B, by means of pressurizing force given by an upper ram33 and a lower ram 35 of a press machine, pressing the mixed powder 23filled in the mold die 25 to mold the compressed powder body 37 iscarried out ((ii) molding step). Subsequently, as shown in FIG. 6C, thecompressed powder body 37 is detached from the mold die 25 and heated ina heating furnace 39 such as a vacuum furnace or an atmospheric furnaceso as to evaporate and remove the wax and sinter the compressed powderbody 37 ((iii) heating step). Thereby, the metal structure 15 made ofthe sintered compressed powder body 37 is formed.

In the course of the (iii) heating step, the metal included in thecompressed powder body 37 fuses together and/or carries outinterdiffusion in itself to form the structure main body 19 to leave thefine pores 19 a. Simultaneously the oxide ceramic or the carbide ceramicincluded in the compressed powder body 37 is made filled into the pores19 a of the structure main body 19 to form the spherical hard particles21. The structure of the structure main body 19 formed in such a wayinherently allows the spherical hard particles 21 to rotate in the pores19 a.

Next, actions and effects of the second embodiment will be describedhereinafter.

As the fine pores 19 a of the structure main body 19 are filled with thehard particles 21 in a rotatable condition, the hard particles 21exposed out of the surface of the structure main body 19 rotate withinthe fine pores 19 a when the outer peripheral surface of the metalstructure 15 rubs against the inner peripheral surface of the oppositeengine component 17. Thereby the rotating hard particles 21 make themetal structure 15 exhibit a lubrication action without lubrication oil.Therefore, regardless of whether the temperature of the atmosphere inuse of the metal structure 15 is high or low, adhesive wear of the metalstructure 15 can be sufficiently suppressed.

Although the invention has been described above by reference to certainembodiments of the invention, the invention is not limited to theembodiments described above. Modifications and variations of theembodiments described above will occur to those skilled in the art, inlight of the above teachings.

1. A protective coating for protecting a component from wear,comprising: a base coating consisting essentially of a metal andincluding a pore; and a spherical particle filling the pore, at least asurface of the spherical particle consisting essentially of a ceramic.2. The protective coating of claim 1, wherein the base coating is formedby executing discharge deposition from a working electrode consistingessentially of the metal onto the component with applying the componentas a workpiece.
 3. The protective coating of claim 1, furthercomprising: a fusion part covering an interface toward the component,the fusion part having a grading composition ratio grading toward thecomponent.
 4. The protective coating of claim 3, wherein the fusion partis 3 μm or more and 20 μm or less in thickness.
 5. A component appliedto a gas turbine engine, comprising: a main body having a subject site;a base coating covering the subject site, the base coating consistingessentially of a metal and including a pore; and a spherical particlefilling the pore, at least a surface of the spherical particleconsisting essentially of a ceramic.
 6. The component of claim 5,wherein the base coating is formed by executing discharge depositionfrom a working electrode consisting essentially of the metal onto themain body with applying the main body as a workpiece.
 7. The componentof claim 5, further comprising: a fusion part covering an interfacetoward the main body, the fusion part having a grading composition ratiograding toward the main body.
 8. The component of claim 7, wherein thefusion part is 3 μm or more and 20 μm or less in thickness.
 9. A metalstructure applied to a site subject to rubbing, comprising: a main bodyconsisting essentially of a metal and including a pore; and a sphericalparticle filling the pore, at least a surface of the spherical particleconsisting essentially of a ceramic.
 10. The metal structure of claim 9,wherein the main body and the particle are formed by sintering a mixedpowder of a powder consisting essentially of the metal and a powderconsisting essentially of the ceramic.